Near-field transducer with enlarged region, peg region, and heat sink region

ABSTRACT

A near-field transducer includes an enlarged region having a top side adjacent to a magnetic pole, a base side opposite the top side, and a circumference that extends from proximal to a media-facing surface to distal to a media-facing surface. The near-field transducer includes a peg region in contact with a region of the bas side of the enlarged region, the peg region extending from the enlarged region towards the media-facing surface. The near-field transducer also includes a heat sink region having a contact side, a base side, and a circumference that extends from proximal to the media-facing surface to distal from the media-facing surface. The contact side of the heat sink region is in thermal contact with both the peg region and at least a region of the base side of the enlarged region.

CROSS REFERENCE TO RELATED CASES

This is a continuation of U.S. patent application Ser. No. 13/961,638,filed Aug. 7, 2013, which is hereby incorporated by reference in itsentirety.

SUMMARY

Embodiments are directed to a near-field transducer comprising anenlarged region having a top side adjacent to a magnetic pole, a baseside opposite the top side, and a circumference that extends fromproximal to a media-facing surface to distal from the media-facingsurface. The near-field transducer also includes a peg region in contactwith at least a portion of the base side of the enlarged region andextending from the enlarged region towards the media-facing surface anda heat sink having a contact side and a base side, and a circumferencethat extends from proximal to the media-facing to distal from themedial-facing surface. The contact side of the heat sink is in thermalcontact with both the peg region and at least a portion of the base sideof the enlarged region.

Embodiments are directed magnetic recording system comprising a harddrive slider that includes a near-field transducer. The near-fieldtransducer comprises an enlarged region having a top side adjacent to amagnetic pole, a base side opposite the top side, and a circumferencethat extends from proximal to a media-facing surface to distal from themedia-facing surface. A peg region is in contact with at least a regionof the base side of the enlarged region and extends from the enlargedregion towards the media-facing surface. A heat sink region has acontact side and a base side, and a circumference that extends fromproximal to the media-facing to distal from the medial-facing surface.The contact side of the heat sink region is in thermal contact with boththe peg region and at least a region of the base side of the enlargedregion.

The above summary is not intended to describe each disclosed embodimentor every implementation of the present disclosure. The figures and thedetailed description below more particularly exemplify illustrativeembodiments

BRIEF DESCRIPTION OF THE DRAWINGS

Throughout the specification reference is made to the appended drawings,where like reference numerals designate like elements, and wherein:

FIG. 1 is a perspective view of a hard drive slider that includes adisclosed near-field transducer.

FIG. 2 is a more detailed front view of the hard drive slider shown inFIG. 1.

FIG. 3 is a side cross-sectional view of a provided near-fieldtransducer and waveguide according to an example embodiment;

FIGS. 4A-4C are plan views of embodiments of provided near-fieldtransducers.

FIG. 4D is a plan view of FIG. 4A with various modeled parametersidentified.

FIGS. 5A-5D are graphs of media to head temperature (“MH”) ratio,thermal gradient (“TG”), full width at 80% maximum (“FW80”), andtemperature rise vs. heat sink disk diameter (in nm) for an embodiedprovided near-field transducer.

FIGS. 6A-6C are graphs of MH ratio, TG, and FW80 ratio vs. peg thicknessfor an embodied provided near-field transducer.

FIGS. 7A-7C are graphs of MH ratio, TG, and FW80 vs. heat sink diskthickness (in nm) for an embodied provided near-field transducer.

FIGS. 8A-8C are graphs of MH ratio, TG, and FW80 vs. peg width for anembodied provided near-field transducer.

FIGS. 9A-9C are graphs of MH ratio, TG, and FW80 vs. peg break pointlength (in nm) for an embodied provided near-field transducer.

FIGS. 10A-10C are graphs of MET ratio, TG, and FW80 vs. HF offset as afunction of various peg lengths (in nm) for an embodied providednear-field transducer.

The figures are not necessarily to scale. Like numbers used in thefigures refer to like components. However, it will be understood thatthe use of a number to refer to a component in a given figure is notintended to limit the component in another figure labeled with the samenumber.

DETAILED DESCRIPTION

In the following description, reference is made to the accompanying setof drawings that form a part of the description hereof and in which areshown by way of illustration several specific embodiments. It is to beunderstood that other embodiments are contemplated and may be madewithout departing from the scope of the present disclosure. Thefollowing detailed description, therefore, is not to be taken in alimiting sense.

Unless otherwise indicated, all numbers expressing feature sizes,amounts, and physical properties used in the specification and claimsare to be understood as being modified in all instances by the term“about.” Accordingly, unless indicated to the contrary, the numericalparameters set forth in the foregoing specification and attached claimsare approximations that can vary depending upon the desired propertiessought to be obtained by those skilled in the art utilizing theteachings disclosed herein. The use of numerical ranges by endpointsincludes all numbers within that range (e.g. 1 to 5 includes 1, 1.5, 2,2.75, 3, 3.80, 4, and 5) and any range within that range.

Various embodiments disclosed herein are generally directed to systemsand apparatuses that facilitate coupling a laser diode to a magneticwriter that includes a magnetic write head. The systems and apparatusesinclude a plasmonic near-field transducer for heat-assisted magneticrecording (HAMR). Plasmonic near-field transducers can generate a largeamount of heat in their writing tip. Disclosed are apparatuses andmethods directed to managing heat buildup in the writing tip ofplasmonic near-field transducers for heat-assisted magnetic recording.

The present disclosure is generally directed to read-write heads used inmagnetic recording devices such as hard drives. In particular, thisdisclosure relates to heat-assisted magnetic recording (HAMR), which canbe used to increase areal data density of magnetic media. In a HAMRdevice, information bits are recorded in a storage layer at elevatedtemperatures in a specially configured magnetic media. The use of heatcan overcome superparamagnetic effects that might otherwise limit theareal data density of the media. As such, HAMR devices may includemagnetic write heads for delivering electromagnetic energy to heat asmall confined media area (spot size) at the same time the magneticwrite head applies a magnetic field to the media for recording.

One way to achieve a tiny confined hot spot is to use an opticalnear-field transducer (NFT), such as a plasmonic optical antenna or anaperture, located near an air-bearing surface of a hard drive slider.Light may be launched from a light source (e.g., a laser diode) intooptics integrated into a slider. An example of such integrated opticsincludes a waveguide formed from core and cladding layers with highcontrast between respective refractive indices. Light propagating in thewaveguide may be directed to an optical focusing element, such as aplanar solid immersion mirror (PSIM). The PSIM may concentrate theenergy into a NFT. The NFT causes the energy to be delivered to themedia in a very small spot.

A waveguide, NFT, and PSIM are examples of integrated optical devicesthat are formed within the slider. The field of integrated opticsgenerally relates to the construction of optics devices on substrates,sometimes in combination with electronic components, to producefunctional systems or subsystems. For example, light may be transferredbetween components via waveguides that are built up on a substrate usinglayer deposition techniques. These waveguides may be formed as a layerof materials, with a middle core layer having a relatively highrefractive index, and top/bottom cladding layers of relatively lowrefractive index. Other optical components may be formed in similarfashion, including the NFT and PSIM discussed above.

In a HAMR slider, light is launched into these integrated opticscomponents from a light source such as a laser diode. One way to launchlight into a slider is from an externally mounted laser via an opticalwaveguide or grating coupler fabricated in a slider. Another way is toplace a laser light source, such as a laser diode, into the slider,called laser-in-slider (LiS) light delivery. In laser-in-sliderconfigurations, light is launched from the emitting facet of a laserdiode into an optical waveguide. Laser-in-slider light delivery can beintegrated at a wafer level and may be suitable for mass production.

FIG. 1 is a perspective view of a hard drive slider that includes adisclosed plasmonic near-field transducer (NFT). HAMR slider 100includes laser diode 102 located on top of HAMR slider 100 proximate totrailing edge surface 104 of HAMR slider 100. Laser diode 102 deliverslight proximate to read/write head 106, which has one edge onair-bearing surface (also referred to as “media-facing surface”) 108 ofHAMR slider 100. Air-bearing surface 108 is held proximate to a movingmedia surface (not shown) during device operation.

Laser diode 102 provides electromagnetic energy to heat the media at apoint near to read/write head 106. Optical coupling components, such asa waveguide 110, are formed integrally within HAMR slider 100 to deliverlight from laser diode 102 to the media. In particular, local waveguide110 and NFT 112 may be located proximate read/write head 106 to providelocal heating of the media during write operations. Laser diode 102 inthis example may be an integral, edge-emitting device, although it willbe appreciated that waveguide 110 and NFT 112 may be used with any lightsource and light delivery mechanisms. For example, a surface emittinglaser (SEL) may be used instead of an edge firing laser.

While the example in FIG. 1 shows laser diode 102 integrated with HAMRslider 100, NFT 112 discussed herein may be useful in any type of lightdelivery configuration. For example, in a free-space light deliveryconfiguration, a laser may be mounted externally to the slider, andcoupled to the slider by way of optic fibers and/or waveguides. Theslider in such an arrangement may include a grating coupler into whichlight is coupled and delivered to slider-integrated waveguide 110 whichenergizes NFT 112.

A HAMR device utilizes the types of optical devices described above toheat a magnetic recording media (e.g., hard disc) in order to overcomesuperparamagnetic effects that limit the areal data density of typicalmagnetic media. When writing to a HAMR medium, the light can beconcentrated into a small hotspot over the track where writing takesplace. The light propagates through waveguide 110 where it is coupled toNFT 112 either directly from the waveguide or by way of a focusingelement. Other optical elements, such as couplers, mirrors, prisms,etc., may also be formed integral to the slider. The optical elementsused in HAMR recording heads are generally referred to as integratedoptics devices.

As a result of what is known as the diffraction limit, opticalcomponents cannot be used to focus light to a dimension that is lessthan about half the wavelength of the light. The lasers used in someHAMR designs produce light with wavelengths on the order of 700-1550 nm,yet the desired hot spot is on the order of 50 nm or less. Thus thedesired hot spot size is well below half the wavelength of the light.Optical focusers cannot be used to obtain the desired hot spot size,being diffraction limited at this scale. As a result, NFT 112 isemployed to create a hotspot on the media.

NFT 112 is a near-field optics device designed to reach local surfaceplasmon resonance at a designed wavelength. A waveguide and/or otheroptical element concentrates light on a transducer region (e.g., focalpoint) where NFT 112 is located. NFT 112 is designed to achieve surfaceplasmon resonance in response to this concentration of light. Atresonance, a high electric field surrounds NFT 112 due to the collectiveoscillations of electrons at the metal surface. Part of this field willtunnel into a storage medium and get absorbed, thereby raising thetemperature of a spot on the media as it being recorded. NFTs generallyhave a surface that is made of a material that supports surface plasmons(“plasmonic metal”) such as aluminum, gold, silver, copper, or alloysthereof. They may also have other materials but they must have amaterial that supports surface plasmons on their outer surface.

FIG. 2 is a front view of a disclosed apparatus showing electrical andoptical interface features of slider assembly 200 that mates with anedge-emitting laser diode (e.g., laser diode 102 in FIG. 1). Cavity 212,solder bumps 214, waveguide input 216, waveguide 210, and air-bearingsurface 208 seen here, were previously illustrated in FIG. 1. Solderbumps 214 on slider assembly 200 are configured to interface with theplurality of solder pads on the lower surface of a laser diode. Thelaser diode may include an output facet on one end that launches lightinto waveguide input 216 of waveguide 210 for delivery to the recordingmedia. Integrated optics associated with light delivery may includecoupling elements, beam expanders 222, collimators, focusing elements226, such as PSIM, concentrating elements, 228 such as a plasmonicnear-field transducer focused adjacent to focal point 230. Furthermore,located at the edge of cavity 212 between the laser diode and waveguideinput 216 is gap 215. The size of gap 215 may depend on the alignment ofthe laser diode to cavity 212, but a typical size may be from about0.25-1.0 μm and up to about 10 μm. Gap 215 may also have an aspect ratioof about 5 to 6. The aspect ratio is the ratio between depth of cavity212 and the width of cavity 212.

NFTs that include an enlarged region and a peg region have beendisclosed. In the context of describing an NFT, the term “region” isused interchangeably with “portion” and refers to a boundedthree-dimensional feature in which the boundaries may either be physicalboundaries or may be arbitrarily chosen for exemplary reasons. TheseNFTs can include a disk-shaped enlarged region that can be made of aplasmonic metal and is configured to receive light from a laser diode.The peg region is in optical and/or electrical communication with thedisk-shaped enlarged region and I creates a focal point for the energyreceived by the enlarged region. In the context of describing an NFT,the term “disk” refers to three-dimensional shapes that include acylinder, a base side, and a top side that may or may not be in a planeparallel with the base side.

Temperature increase inside the peg region of NFTs is a challenge inHAMR write heads. It would be desirable to design an NFT that has lessof a temperature increase than NFTs known in the art. To reduce thetemperature of the peg region of an NFT the thermal resistance of thepeg should be reduced. However, the thermal resistance of the peg mustalso be reduced without substantially compromising the transducerperformance (i.e. coupling efficiency). The coupling efficiency is thepercentage of energy absorbed into the media surface, divided by theenergy input at the incident plane of the PSIM from the energy source.

Also, related to the temperature increase is the thermal resistance.Thermal resistance of an object is directly proportional to the lengthof the object and inversely proportional to the cross-sectional area andthermal conductivity of the object (Fourier's Law). A typical materialfor constructing an NFT is gold, which has good mechanical andoptical/plasmonic properties compared to other materials. Varying theNFT material may not substantially increase the thermal conductivity.Therefore, other means are required for reducing the thermal resistanceof the peg region. In one aspect, to minimize thermal resistance thelength of the peg region may be decreased. In another aspect, tominimize thermal resistance the cross-sectional area of the peg may alsobe increased. However, the cross-sectional area of the peg at theair-bearing surface, nearest the recording media, is dictated by theparameters required for magnetic recording. Additionally, specificwavelength of light from the laser diode dictates the size of theenlarged region of the NFT and the peg length in order to get optimal(maximum) coupling efficiency of the laser light to the NFT.

The present disclosure relates to systems and apparatuses that includeplasmonic near-field transducers. FIG. 3 is a side cross-sectional viewof an exemplary provided near-field transducer and waveguide accordingto an example embodiment that illustrates features disclosed herein. Inreference now to FIG. 3, a cross-sectional view shows details of an NFT310 and waveguide 302 of a HAMR apparatus 300 according to an exampleembodiment. The NFT 310, waveguide 302, and other components are builton a substrate plane, which is parallel to the xy-plane in this view.NFT 310 is located proximate a media-facing surface 314 (e.g., ABS),which is held near a recording medium 308 during device operation, e.g.,magnetic disk. In the orientation of FIG. 3, the media-facing surface314 is arranged parallel to the x-y plane. Elongated waveguide core 303may be disposed proximate the NFT 310, NFT 310 being located at or nearthe media-facing surface 314.

Waveguide core 303 is shown configured as a planar waveguide, and issurrounded by cladding layers 307 and 309 that have different indices ofrefraction than core 303. Other waveguide configurations may be usedinstead of a planar waveguide, e.g., channel waveguide. Light 304propagates through the waveguide core 303 along the negativey-direction. Electrical field lines 306 emanate from the waveguide core303 and excite NFT 310. NFT 310 delivers surface plasmon-enhanced,near-field electromagnetic energy along the negative y-direction whereit exits at the media-facing surface 314. This may result in a highlylocalized hot spot (not shown) on media 308. Further illustrated in FIG.3 is magnetic recording pole 312 that is located alongside NFT 310.Magnetic pole 312 generates a magnetic field (e.g., perpendicular field)used in changing the magnetic orientation of the hotspot during writing.

NFT 310 includes enlarged region 310 b of plasmonic material (e.g.,gold, silver, copper, and combinations or alloys thereof). Enlargedregion 310 b has top side 310 e adjacent to magnetic pole 312, base side310 f opposite top side 310 e, and a circumference that extends fromproximal 310 c to media-facing surface 314 to distal the media-facingsurface 310 d (for example, along the y-axis). The NFT 310 furtherincludes peg region 310 a of plasmonic material that is in contact withat least a portion of base side 310 f of enlarged region. Peg region 310a extends from enlarged region 310 b towards media-facing surface 314.As will be described in greater detail below, the projection of enlargedregion 310 b onto the xy-plane is narrowed at the output end.

NFT 310 also includes heat sink 320. Heat sink 320 has contact side 320a, base side 320 b and a circumference that extends from proximalmedia-facing surface 314 to distal from media-facing surface 314 in amanner analogous to that of enlarged region 310 b. Contact side 320 a ofheat sink 320 is in thermal contact with both peg region 310 a and atleast a portion of base side 310 f of enlarged region 310. FIG. 3 showsa line between enlarged region 310 b and peg region 310 a. This line isfor illustrative purposes only. Commonly, enlarged region 310 b andenlarged region 310 a are one piece and make up NFT 310. Thus, pegregion 310 a may extend from part of the circumference of NFT 310 aswill be illustrated later.

NFT 310 is excited by a waveguide mode of the planar waveguide 302,polarized with dominant electric field 306 normal to the plasmonic metalsurfaces of the NFT 310, e.g. circumference of enlarged region 310 b.Enlarged region 310 b also includes top side 310 e that faces, and inthis example directly contacts, magnetic pole 312. Enlarged region 310 bof NFT 310 is shaped to condense the field and the peg 310 a is designedto resonate such that the NFT efficiency is enhanced on one hand, and onthe other hand scattering of the field is reduced along thecircumference of the enlarged region 310 b.

Excitation of NFT 310 may occur over a large region of enlarged region310 b and heat sink region 320, however, there is no limitation as towhere or how NFT 310 may be excited by energy delivered by the waveguide302. Generally, it will be understood that NFT 310 is designed to directthe surface plasmons from the output end of peg region 310 a to media308 when media 308 is proximate to the media-facing surface 314. The endpeg region 310 a protrudes out from elongated region 310 b nearmedia-facing surface 314. This protrusion can improve NFT efficiency andthermal gradient for writing sharp magnetic transitions. Surface plasmonwaves are generated mainly at surfaces of peg region 310 a and enlargedregion 310 b nearest planar waveguide core 303. The tip of the pegregion may have different cross-section and or size from the body of thepeg region.

The waveguide mode is TE₀₀, which is fundamental and transverse-electricpolarized. The dominant electric field 306 is along x-direction andnormal to base side 310 f of enlarged region 310. The mode index ofdielectric waveguide 302 is close to that of the surface-plasmon waves,therefore surface-plasmon waves are efficiently excited on enlargedregion 310 b and heat-sink region 320. The elongated peg 310 a functionsas a monopole antenna. At resonance, it interacts with the dielectricwaveguide mode as well as the surface-plasmon waves generated on thecircumferences of enlarged region 310 b and heat sink region 320, whichpulls the field toward itself and delivers the optical energy into therecording media 308. The presence of heat sink 320 helps to increase thecoupling efficiency and to reduce the temperature of the writing tip ofpeg region 310 a

FIGS. 4A-4C are plan views of various embodiments of provided NFTs. FIG.4A is an illustration of one embodiment, 400A. NFT 400A includesenlarged region 410A that has top side 414A adjacent to a magnetic pole(not shown) and base side 424A opposite (but not necessarily parallelto) top side 414A. Enlarged region has a circumference that extends fromproximal media-facing surface 430A to distal media-facing surface 430A.In the embodiment illustrated in FIG. 4A, the circumference iscylindrical, having a cross-section parallel to the base side of theenlarged region that is circular, however other shapes of enlargedregion are also contemplated. In some embodiments, the circumference canbe conical. In some embodiments, the circumference of the enlargedregion may be elliptical.

When the circumference of the enlarged region has circular or ellipticalcross-section, the enlarged region can be sometimes referred to as adisk. In some embodiments, a plane that includes the top side of theenlarged region can be at an angle with respect to a plane that includesthe base side of the enlarged region. In some other embodiments, thecircumference of the enlarged region may be the sides of a regular orirregular rectangular or triangular parallelepiped having across-section that is a square, rectangle, triangle, regular orirregular polygon. In some embodiments, the area of the top side of theenlarged region is substantially the same as the area of the base sideof the enlarged region. More complex geometrical shapes of the enlargedregion can also be within the scope of this disclosure.

NFT 400A also has peg region 412A that is in contact with at least aportion of base side 424A of enlarged region 410A and extends fromenlarged region 410A towards media-facing surface 430A. As shown in FIG.3, peg region 412A is an extension of enlarged region 410A. FIG. 4Ashows the end of peg region 412A (the region closest to media-facingsurface 430A) as having a non-tapered end. However, the end may betapered to provide a smaller surface area at the tip of the peg regionto better focus the energy from the NFT onto a small spot on the media.

NFT 400A includes heat sink 420A that has contact side 424A and baseside 426A. Heat sink 420A also has a circumference that extends fromproximal media-facing surface 430A to distal media-facing surface 430A.Contact side 424A of heat sink 420A is in thermal contact with both pegregion 412A and at least a portion of base side 424A of enlarged region410A. When the circumference of the heat sink region is circular orelliptical, the heat sink region can be sometimes referred to as a disk.In some embodiments, the area of the contact side of the heat sinkregion is the same as the area of the base side of the heat sink region.

FIG. 4B is an illustration of another embodiment of a provided NFT. NFT400B includes enlarged region 410B that has top side 414B adjacent to amagnetic pole (not shown) and base side 424B opposite (but notnecessarily parallel to) top side 414B. Enlarged region 410B has acircumference that extends from proximal media-facing surface 430B todistal media-facing surface 430B. NFT 400B also has peg region 412B thatis in contact with at least a region of base side 424B of enlargedregion 410B and extends from enlarged region 410B towards media-facingsurface 430B. NFT 400B includes heat sink 420B that has contact side424B and base side 426B. Heat sink 420B also has a circumference thatextends from proximal media-facing surface 430B to distal media-facingsurface 430B. Contact side 424B of heat sink 420B is in thermal contactwith both peg region 412B and at least a portion of base side 424B ofenlarged region 410B. The circumference of enlarged region 410B proximalto media-facing surface 430B is offset in a direction away frommedia-facing surface 430B with respect to heat sink 420B as shown inFIG. 4B. Also the circumference of enlarged region 410B distal tomedia-facing surface 430B is offset away from media-facing surface 430Bwith respect to heat sink 420B.

FIG. 4C is an illustration of another embodiment of a provided NFT. NFT400C includes enlarged region 410C that has top side 414C adjacent to amagnetic pole (not shown) and base side 424C opposite (but notnecessarily parallel to) top side 414C. Enlarged region has acircumference that extends from proximal media-facing surface 430C todistal media-facing surface 430C. NFT 400C also has peg region 412C thatis in contact with at least a region of base side 424C of enlargedregion 410C and extends from enlarged region 410C towards media-facingsurface 430C. NFT 400C includes heat sink 420C that has contact side424C and base side 426C. Heat sink 420C also has a circumference thatextends from proximal media-facing surface 430C to distal media-facingsurface 430C. Contact side 424C of heat sink 420C is in thermal contactwith both peg region 412C and at least a portion of base side 424C ofenlarged region 410C. The circumference of enlarged region 410C proximalto media-facing surface 430C is offset in a direction away frommedia-facing surface 430C with respect to heat sink 420C as shown inFIG. 4C. The circumference of enlarged region 410C distal tomedia-facing surface 430C is not offset from media-facing surface 430Cwith respect to the circumference of the heat sink region 420C proximalto media-facing surface 430C.

The enlarged region and the peg region of disclosed near-fieldtransducers can comprise a substrate which has been at least partiallycovered with a thin layer of plasmonic material. The substrate cancomprise any material capable of supporting a thin layer of plasmonicmaterial. Typical substrates include silicon wafers, inorganic andorganic dielectrics, polymer dielectrics, glass, non-conductive metalsand ceramics. Typical plasmonic materials include at least one ofaluminum, silver, copper, gold, and alloys thereof. Gold is a typicallyused material due to its good mechanical properties, coupling efficiencyand its ability to generate surface plasmons. The heat sink region caninclude materials that have a high heat conductivity. Materials usefulfor the heat sink region include gold, silver, or alloys thereof.

During the operation of the plasmonic near-field transducer, theplasmonic near-field transducer experiences a temperature rise. Modeling(finite element analysis of heat flow) has shown that the temperaturerise is highest in the peg region of the near-field transducer. Themodels indicate that the electromagnetic field generated within thenear-field transducer during the recording operation is highest withinthe peg region. Models show that the amplitude of the electromagneticfield is directly proportional to the energy absorption level. Thedisclosed plasmonic near-field transducers may include a heat sinkregion for cooling the NFT through improved heat dissipation from thepeg region to the heat sink region.

Finite element analysis of various near-field transducer configurationswas performed to identify the most important structural features of thenear-field transducers that provide for improved (e.g., maximum)performance efficiency in HAMR recording heads. The responses ofinterest were recording media to recording head temperature ratio (“MH”ratio), thermal gradient (“TG”), and full width at 80% maximum thermalspot size (“FW80”) in the media heated with the modeled transducers.Based upon modeling, it was determined that NFTs with a combination ofhigher MH ratio, and lower TG and FW80, provide for improved performanceefficiency. The models were based upon designs of provided near-fieldtransducers made in SiO₂. The modeled NFTs had circular cross-sectionsand were generally for the structure of NFT illustrated in FIG. 4A. Forthe different models with results disclosed herein, the variables wereheat sink disk diameter in nm (451 in FIG. 4D), peg thickness in nm (452in FIG. 4D), thickness of heat sink with various peg thicknesses (453 inFIG. 4D), peg width in nm (454 in FIG. 4D) and peg length from the breakpoint in nm (455 in FIG. 4D). In the modeled NFT, the disk diameter was280 nm, the peg height was 20 nm, the peg thickness was 25 nm, and theclosest distance of the sunken region to the waveguide core was 25 nm.In this disclosure, the term “break point” refers to the location in apeg region of a near-field transducer that is on the circumference ofthe enlarged region of a near-field transducer nearest to an air-bearingsurface.

FIGS. 5A-5C show the modeled effect of heat sink disk diameter on MHratio, TG, and FW80 for a silica NFT as illustrated in FIG. 4A. FIG. 5Dillustrate the relationship of heat sink disk diameter to temperaturerise per mW of input laser power. To maximize MH, temperature rise permW input laser power, and to minimize FW80, it can be seen that a diskdiameter of from about 150 nm to about 350 nm, from about 240 nm toabout 260 nm, or about 250 nm gives the best combination of desiredproperties.

FIGS. 6A-6C show the modeled effect of peg thickness on MH ratio, TG,and FW80 for a silica NFT as illustrated in FIG. 4A. In order tomaximize MH ratio and TG and to minimize FW80, the best peg thickness isfrom about 25 nm to about 40 nm or about 35 nm.

FIGS. 7A-7C show the modeled effect of heat sink disk thickness on MHratio, TG, and FW80 for two different peg thicknesses (25 nm and 30 nm).The 30 nm thick peg is seen to have a higher MH ratio but lower TG forall thicknesses of heat sink disks. A thicker peg gives a larger thermalspot (FW80). In order to maximize MH ratio and TG and to minimize FW80,a heat sink disk thickness of from about 10 nm to about 80 nm, fromabout 30 nm to about 60 nm, from about 35 nm to about 40 nm, or about 35nm is desired along with a peg thickness of from about 25 nm to about 30nm.

FIGS. 8A-8C show the modeled effect of peg width on MH ratio, TG, andFW80. To maximize MH ratio and TG, and minimize FW80, a peg width offrom about 35 nm to about 40 nm or about 35 nm has the best combinationof properties.

FIGS. 9A-9C show the modeled effect of peg length from the break point(“Peg BP”) on MH ratio, TG, and FW80. Here the MH ratio is highest at alower peg length from the break point, but the TG and FW80 increase withhigher peg length from the break point. The peg region can extend fromabout 10 nm to about 30 nm from the break point on the enlarged regionof the NFT.

NFT configurations that have an offset (shown as 464 in FIG. 4B) of thecenter of the enlarged region with respect to the center of the heatsink disk as shown in FIG. 4B were modeled as a function of threedifferent peg lengths from the break point (“peg BP”)—15 nm, 20 nm, and25 nm. An offset of 0 indicates that the heat sink region lines up withthe enlarged region as shown in FIG. 4A. A positive offset indicates theenlarged region of the NFT is offset towards the media-facing surface. Anegative offset indicates the enlarged region of the NFT is offset awayfrom the media-facing surface. The heat sink disk diameter was 280 nm,the heat sink disk thickness was 50 nm, the peg thickness was 25 nm, andthe peg width was 45 nm. The overmill (shown as 462 in FIG. 4B) was 6nm. The modeling results show a 15 nm peg length to break point with a−20 nm heat sink offset gives the best reliability of performance.

The effect of overhang of the enlarged region of the NFT compared to theheat sink region (460 in FIG. 4B) was modeled using an NFT with astructure as shown in FIG. 4B with a various heat sink disk diameters, aheat sink thickness of 50 nm, a peg thickness of 25 nm, a peg width of45 nm, a peg length from the break point of 15 nm, an offset of −15 nm,with an overmill of 6 nm, and various overhangs in which the distalcircumference of the enlarged region of the NFT over hangs the distalcircumference of the heat sink region of the NFT (see 460 in FIG. 4B).Table 1 shows the modeled MH ratio, TG, and FW80 as a function of heatsink diameter and subsequently overhang.

TABLE 1 Modeled MH ratio, TG, and FW80 Changes as Function of OverhangHS Diameter (nm) Overhang (nm) MH ratio TG FW80 265 0 −3.45% +1.37%−1.94% 280 15 0 0 0 310 45 +2.74% −3.20% −3.22%The data in Table 1 show that overhang can improve the MH ratio butreduce TG and increase FW80.

All references and publications cited herein are expressly incorporatedherein by reference in their entirety into this disclosure except to theextent they may directly contradict this disclosure. Although specificembodiments have been illustrated and described herein, it will beappreciated by those of ordinary skill in the art that a variety ofalternate and/or equivalent implementations can be substituted for thespecific embodiments shown and described without departing from thescope of the present disclosure. This application is intended to coverany adaptations or variations of the specific embodiments discussedherein. Therefore, it is intended that this disclosure be limited onlyby the claims and the equivalents thereof. All references cited withinare herein incorporated by reference in their entirety.

What is claimed is:
 1. An apparatus, comprising: a near-field transducerof a heat-assisted magnetic recording slider comprising: a peg regionformed from plasmonic material; an enlarged region formed from plasmonicmaterial and having a top side configured to contact a magnetic pole ofthe slider, a base side opposite the top side, and a circumference thatextends from proximal an air bearing surface (ABS) of the slider todistal the ABS; and a heat sink region having a contact side, a baseside, and a circumference that extends from proximal the ABS to distalthe ABS, wherein the contact side of the heat sink region is in physicalcontact with at least a region of the base side of the enlarged region,and the heat sink region is formed from plasmonic material andconfigured to enhance coupling efficiency of the near-field transducer;wherein the circumference of the enlarged region is offset from thecircumference of the heat sink region.
 2. The apparatus of claim 1,wherein the circumference of the enlarged region is offset from thecircumference of the heat sink region relative to the ABS.
 3. Theapparatus of claim 1, wherein the circumference of the enlarged regionis offset from the circumference of the heat sink region in a directionaway from the ABS.
 4. The apparatus of claim 1, wherein a distalcircumference of the enlarged region overhangs a distal circumference ofthe heat sink region.
 5. The apparatus of claim 1, wherein an overmillregion is defined between the proximal circumferences of the enlargedand heat sink regions.
 6. The apparatus of claim 1, wherein an area ofthe top side of the enlarged region is the same as an area of the baseside of the enlarged region.
 7. The apparatus of claim 1, wherein anarea of the contact side of the heat sink region is the same as an areaof the base side of the heat sink region.
 8. The apparatus of claim 1,wherein the heat sink region has a diameter of about 150 nm to about 350nm.
 9. The apparatus of claim 1, wherein the heat sink region has adiameter of about 240 nm to about 300 nm.
 10. The apparatus of claim 1,wherein the heat sink region has a thickness of about 30 nm to about 50nm.
 11. An apparatus, comprising: a slider of a heat-assisted magneticrecording head comprising: a writer comprising a write pole; an opticalwaveguide; and a near-field transducer optically coupled to the opticalwaveguide, the near-field transducer comprising: a peg formed fromplasmonic material; an enlarged disk formed from plasmonic material andhaving a top side configured to contact the write pole of the writer, abase side opposite the top side, and a circumference that extends fromproximal an air bearing surface (ABS) of the slider to distal the ABS;and a heat sink disk having a contact side, a base side, and acircumference that extends from proximal the ABS to distal the ABS,wherein the contact side of the heat sink disk is in physical contactwith at least a region of the base side of the enlarged disk, and theheat sink disk is formed from plasmonic material and configured toenhance coupling efficiency of the near-field transducer; wherein thecircumference of the enlarged disk is offset from the circumference ofthe heat sink disk.
 12. The apparatus of claim 11, wherein thecircumference of the enlarged disk is offset from the circumference ofthe heat sink disk relative to the ABS.
 13. The apparatus of claim 11,wherein the circumference of the enlarged disk is offset from thecircumference of the heat sink disk in a direction away from the ABS.14. The apparatus of claim 11, wherein a distal circumference of theenlarged disk overhangs a distal circumference of the heat sink disk.15. The apparatus of claim 11, wherein an overmill region is definedbetween the proximal circumferences of the enlarged and heat sink disks.16. The apparatus of claim 11, wherein an area of the top side of theenlarged disk is the same as an area of the base side of the enlargeddisk.
 17. The apparatus of claim 11, wherein an area of the contact sideof the heat sink disk is the same as an area of the base side of theheat sink disk.
 18. The apparatus of claim 11, wherein the heat sinkdisk has a diameter of about 150 nm to about 350 nm.
 19. The apparatusof claim 11, wherein the heat sink disk has a diameter of about 240 nmto about 300 nm.
 20. The apparatus of claim 11, wherein the heat sinkdisk has a thickness of about 30 nm to about 50 nm.